30 km is quite a bit of the forest but with half the world cup course to start with
50 km is same start but with a bit of moorland stuff as well, think you might find it a little short
100km same start and then some of the best moorland singletrack in the area, if it's dry it will be a real blast, little bit of back roads to get you back to Dalby and some big climbs but I've tried to keep it do'able and fun...just long
I'd do the 100km and cut it short before going out to Scarboro' if you're feeling it...